CAREER: Study of Emergent Ground States and Bosonic Excitations in Materials with Strong Spin-Lattice Coupling

*我们目前对材料的理解是，它们是原子核的刚性晶格，可以振动，但主要是作为带电电子运动和自旋的公正背景。在原子核振动与电子自旋强烈相互作用的材料中，最近报道了许多新的行为，这些行为知之甚少，但对未来的电子设备和能源技术可能有用。目前的项目试图通过识别关键模型系统来理解这些行为，在这些系统中，强自旋-晶格耦合的影响是突出的，并且可以在没有额外复杂因素的情况下进行研究。利用伊利诺伊大学的设备和专业知识，人们正在制备新型材料的粉末和大单晶，随后，国家实验室也在使用尖端设备研究原子运动和磁性。研究小组特别关注那些从初步探索中被认为最有希望的行为。这项工作与理解和控制常见材料特性有关，并将有助于进一步发展一些新技术。这个项目的一个主要主题也是推动物质的新状态，这些状态可能具有无数有用或有趣的特性。这些活动为培训研究生和本科生学习材料生产和表征方法提供了理想的环境，这符合当前国家的优先事项。首席研究员还在伊利诺伊大学开设了一门关于研究材料的实验方法的研究生课程，为下一代科学家提供更多的研究机会，并促进学生研究人员之间的合作。通过一系列的公开讲座和在线交流，首席研究员还帮助教育普通民众关于材料科学，磁学和现代物质实验探针。*技术摘要*本项目旨在识别、表征和控制晶格自由度和自旋自由度之间强耦合的材料的磁性。一项联合材料开发和实验计划正在进行中，其中将采用特定的材料策略来合成模型自旋-晶格耦合系统并生长晶体，随后利用国家实验室的设施通过中子散射和介子自旋来研究它们。为了最大限度地发挥影响，该提案侧重于从初步工作中被认为有希望的四个具体领域。这些包括驱动转换到新的磁场基态，掺杂或压力；研究材料中相分离和长尺度域的有序；探索自旋-晶格耦合如何改变集体激励；创造新的超导体，在自旋和轨道角动量之间有很强的耦合。自旋-晶格耦合效应与广泛的物理主题有关，包括巨响应函数、多铁性、超导性和导热性。目前的工作将通过识别和开发模型材料进一步讨论这些现象，其中自旋-晶格耦合效应可以被隔离，控制和直接研究。通过孤立地研究自旋-晶格耦合效应，本工作将澄清其在更复杂的材料系统中的作用的讨论和理解。

*Non-technical Abstract*Our current understanding of materials is that they are a rigid lattice of atomic nuclei, which can vibrate, but largely serve as an impartial backdrop for the motion and spinning of charged electrons. In materials where the vibrations of nuclei strongly interact with the electron spins, a number of novel behaviors have been recently reported, which are poorly understood but potentially useful for future electronic devices and energy technologies. The current project seeks to understand these behaviors through the identification of key model systems in which the effects of strong spin-lattice coupling are prominent and can be studied without additional complicating factors. Powders and large single crystals of novel materials are being prepared using equipment and expertise at the University of Illinois, and atomic motion and magnetic properties are subsequently being studied using cutting edge facilities at national laboratories. The research team is focusing specifically on behaviors deemed most promising from preliminary explorations. This work is pertinent to the understanding and control of common material properties and will help further the development of a number of new technologies. A major theme of this project is also to drive new states of matter, which might have untold useful or interesting properties. These activities provide an ideal environment for the training of graduate and undergraduate students in the methods of materials production and characterization, which is in line with current national priorities. The principal investigator is also developing a graduate course on experimental methods for studying materials at the University of Illinois, to provide greater understanding for the next generation of scientists of research opportunities open to them and to foster collaboration among student researchers. Through a series of public lectures and online exchanges, the principal investigator is also helping to educate the general populace about the science of materials, magnetism and modern experimental probes of matter.*Technical Abstract*This project seeks to identify, characterize and control the magnetic properties of materials containing a strong coupling between lattice and spin degrees-of-freedom. A joint materials development and experimental program is being pursued, where specific materials strategies will be employed to synthesize model spin-lattice coupled systems and to grow crystals, and subsequently to study them via neutron scattering and muon spin rotation using facilities at national laboratories. To maximize impact, the proposal focuses on four specific areas deemed promising from preliminary work. These include driving transitions to novel magnetic ground states with field, doping or pressure; investigating phase separation and long length-scale ordering of domains in materials; exploring how spin-lattice coupling modifies collective excitations; and creating new superconductors having strong coupling between spin and orbit angular momentum. Spin-lattice coupling effects are relevant to the discussion of a wide range of physics topics, including colossal response functions, multiferroism, superconductivity, and thermal conductivity. The current work will further discussion of these phenomena through the identification and development of model materials, where spin-lattice coupling effects can be isolated, controlled and studied directly. By studying spin-lattice coupling effects in isolation, this work will clarify the discussion and understanding of its role in more complex material systems.